Why is there no cure for the "boils of Egypt"?
Rashi: Because they are dry on the inside and moist on the outside (and there is no cure for dry boils - Bechoros 41a ). 1
Chizkuni: Because, since Hashem struck, who can heal them? 2
Toldos Yitzchak: There is a cure for dry boils, but it is harmful for moist boils. There is a cure for moist boils, but it is harmfuls dry boils. Therefore, one cannot cure them. 3
What is the definition of "Techorim"?
Rashi (in Megilah, 25b): It is hemorrhoids (in the anus). 1
Megilah, Ibid.: The Torah actually writes "u'Va'apolim". However, since that is a more explicit term, we read it "u'va'Techorim".
What is the difference between "Garav" and "Cheres"?
Rashi and Targum Yonasan 1 : They are wet boils (on the outside bur dry on the inside - Rashi, in Emor Vayikra, 21:20) and boils that are dry like clay, respectively.
See Peirush Yonasan.
